Question

1. What are the types of solar collector and mention the primary use of each type?
2. Explain the main difference between hydronic heating system and forced air heating system?
3. In simple words, how passive liquid heating systems work?

Answer 1

Solar collectors are broadly classified as 2 types.

1.Non - concentrating type

• A flat plate collector is a box which is  covered by glass or plastic with a metal absorber plate. This absorber plate will be on bottom side. The glazing, or coating, on this absorber plate helps in better absorbing and retaining of heat. use : heating water in a pool.

• Evacuated tube collectors : most efficient, most costly type of hot water solar collectors. This collectors have glass or metal tubes with a vacuum, allowing them to operate well in colder climates.use : separate the potable water from the non-toxic anti-freeze in the collector

2. concentrating type

• Compound parabollic collector : they are non imaging concentrators. use : have the capability of reflecting to the absorber all of the incident radiation within wide limits
• parabollic dish soalr collector : It is a 2-axis solar tracking system. It concentrate the solar radiations to the thermal receiver placed on the focal point of the dish collector use : parabollic dish engines
• parabollic trough :  These collectors reflect the incoming solar radiation onto its focal line to a receiver that absorbs the concentrated solar energy to increase the temperature of inside fluid.
• Solar tower : works on same principle of solar trough. use : commercial solar tower power plant

Hydronic heating system Vs Forced air heating system

	Forced air heating system	hydronic heating system
Medium	use air	use water
Installation Cost	Low	High
Health & safety	dust and allergens	only water damage. Healthy system.
Energy efficiency	less efficient	more energy efficient
Noise	More	Less

Passive liquid heating systems

These type of systems do not use a pump to circulate water from the collector to storage or other locations.It costs less and have extremely low or no maintenance, but the efficiency is significantly low comparing to an active system. They have three means to circulate water:

• gravity,
• the tendency of hot water to rise above cold water and
• water pressure.

two types of passive systems are there

1. Direct : Simple one.
2. Indirect : complex one

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